U.S. President-elect Donald Trump stands with retired Marine Gen. James Mattis following their meeting at the main clubhouse at Trump National Golf Club in Bedminster, New Jersey, U.S., November 19, 2016.
REUTERS/Mike Segar

If the Democrats choose to oppose the nomination of Gen. James Mattis for Defense Secretary, it's probably not going to go well for them — regardless of the final outcome.

The nomination of the retired Marine general has put Democrats in a bit of a pickle: Since he hasn't been out of uniform for the statutorily required seven years, he requires a waiver from Congress — giving Democrats an opening to oppose a Trump nominee.

But in the case of this nominee, he is more than qualified for the position, having served 44 years in the Marine Corps, where he last retired as the head of the military's Central Command in Tampa, Florida. Even Democratic Rep. Ruben Gallego of Arizona, a Marine veteran who said he would oppose a waiver, called Mattis "exceptionally qualified."

Where does the fight eventually lead?

Democrats can try to hold up the nomination of Mattis and fight against a waiver. As Sen. Kirsten Gillibrand of New York has said, her position is based on maintaining civilian control of the military as a "fundamental principle of American democracy."

The principle is maintained by a 1947 law that requires a military officer to be off active duty for 10 years before leading the Department of Defense. It was amended to seven years in 2008. Mattis, having retired in 2013, would be just more three years shy of that limit if confirmed after Trump takes office.

Interestingly, this wouldn't even be an issue if Trump nominated another reported candidate, retired Army Gen. Jack Keane — an officer who retired in 2003. He said he declined Trump's offer of the position for family reasons. In the case of Keane, he would have easily had the votes from a Republican-controlled Congress, and a former military officer would be leading the department.

But some Democrats don't view Mattis as civilian enough — as if three more years of him serving as a scholar in residence at places like Dartmouth and Stanford or contributing on corporate boards has not given him enough experience outside of uniform.

Mattis' qualifications should not be questioned. If confirmed as Defense Secretary, his legendary status within the ranks would instantly boost morale. His time served at Central Command and Joint Forces Command give him the bona fides to be able to lead a large organization with many different services and civilian workers.

And he would serve as an important check on Trump — and his controversial national security adviser, Lt. Gen. Michael Flynn — on everything from torture to sending US forces into harm's way.

US Marine Corps

That's especially true since Mattis, now 66, has taken to the lecture circuit in recent years and has repeatedly stressed the importance of a commander in chief giving the military a clear political end state — a policy desperately needed when the US still remains in what have been dubbed "forever wars" in Iraq and Afghanistan.

"Secretary of Defense Mattis will never commit anyone into harm's way without the national interests at stake and a plan to win," Nate Fick, a former Marine captain who twice served under Mattis in Afghanistan and Iraq, told Business Insider. "I think that that’s welcome."

Let's just say Democrats decide to go nuclear against the Mattis appointment, and somehow he ends up as Defense Secretary anyway.

Republicans would have plenty of ammunition to criticize their counterparts, especially considering their opposition stems from an arbitrary standard of three years. Though Mattis has offered some colorful, and somewhat controversial, quotes over the years, his military service record is exemplary. His leadership ability isn't in question.

"I think he would be fantastic," Democratic Rep. Seth Moulton of Massachusetts, a former Marine officer who served under Mattis and is open to a waiver, told The Eagle-Tribune. "He has led one of the most significant commands of our nation. He is a deep thinker and a student of history. He has a library of something like 6,000 books. That’s precisely the kind of thoughtfulness and perspective we need in our secretary of defense."

So at the end of the day, the only fight Democrats have against him is a 1947 law they know can easily be waived.

From there, they'd be starting off a new president's term having been beaten back from this opposition, when they would have been better served opposing some of Trump's more controversial picks, such as Ben Carson, his nominee to be Secretary of Housing and Urban Development, or Attorney General-designate Jeff Sessions.

Here's where Democrats really need to decide on what is important. Is it important to maintain a stringent view that Mattis cannot get a waiver? Because if that's the course of action, Trump's next step could be to nominate someone whom Democrats are guaranteed not to like.

Among the names floated during the nominating process were former Sen. Jim Talent, a Republican from Missouri, who served in the Senate for much of the Bush administration. He currently serves on the US-China Economic and Security Review Commission, a group created by Congress that examines the US-China relationship and prepares an annual report on its national-security implications.

Unlike Mattis — who has called the invasion of Iraq a "strategic mistake" — Talent is an Iraq War hawk. Though he wasn't in Congress for the 2002 vote to go to war, he said in 2006 that he still would have invaded Iraq even with the knowledge there were no weapons of mass destruction.

Another civilian name on the reported short list was that of Stephen Hadley, the former national security adviser to President George W. Bush. A controversial figure, Hadley was largely responsible for the false allegation that Iraq tried to buy uranium from Niger prior to the invasion, which made its way into President Bush's 2003 State of the Union speech. He later apologized.

Democrats shouldn't just roll over and play dead on a Mattis appointment. They and their Republican colleagues definitely need to ask some hard questions of Mattis' views on the detention facility at Guantanamo Bay, women in the military, and how he might counter geostrategic foes such as Iran, Russia, and North Korea.

But with former defense secretaries endorsing him for the job (Rumsfeld, Gates, and Panetta, among others), bipartisan support on Capitol Hill, and a large portion of the men and women in uniform rallying around him, Democrats would be wise to oppose Mattis on substantive issues — not the issue of whether his uniform has sat unworn in his closet for long enough.

"Considering the other picks that [Trump] has made, this would be the wrong target" for Democrats to oppose, Panetta said at a national security forum over the weekend.

"I believe that civilian control and civilian involvement in the Defense Department is an important principle, but I also don’t think a military background should be disqualifying," he later told a Washington Post reporter after his talk.

This column does not necessarily reflect the opinion of Business Insider.